<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<body>
<script type="text/javascript">
	
	/*	
	var a = [1,2,3];
	var b = new Array(1,2,3);
	*/
	var a = [];
	var b = new Array(5);
	a.length = 5
	//[ , , , , ]
	alert(a);
</script>
</body>
</html>